feat(raygui): get message box example working

build.zig

@@ -167,6 +167,11 @@ pub fn build(b: *std.Build) !void {
             .path = "examples/core/window_flags.zig",
             .desc = "Demonstrates various flags used during and after window creation",
         },
+        .{
+            .name = "gui_message_box",
+            .path = "examples/gui/message_box.zig",
+            .desc = "Demonstrates showing and hiding a message box",
+        },
         .{
             .name = "raymarching",
             .path = "examples/shaders/raymarching.zig",